POS0810 T FOLLICULAR HELPER CELLS IN BLOOD MIRROR SALIVARY GLAND-INFILTRATING T CELLS IN PRIMARY SJÖGREN’S SYNDROME
Authors: S. Abe, H. Tsuboi, H. Toko, F. Honda, A. Koido, H. Miki, H. Asashima, Y. Kondo, I. Matsumoto
Journal: Annals of the Rheumatic Diseases (2023)

<h3>Background</h3> Although clonal expansion of autoreactive T cells have been identified in the peripheral blood and salivary gland of primary Sjögren's syndrome (pSS) (1), the relationship between peripheral immune environments and inflammatory organs remains still unclear. <h3>Objectives</h3> Here, we examined which T cell subsets in blood share the same T cell receptor (TCR) αβ with T cells infiltrated at labial salivary gland (LSG) in patients with pSS, and evaluated mechanisms of their differentiation. <h3>Methods:</h3> 1) TCR repertoires of each effector memory T cell subset (Th1, Th17, Tfh1, Tfh2, Tfh17) in blood, and LSG-infiltrating T cells obtained from the same pSS patient were analyzed by TCR sequence (<i>n</i>=1). 2) The proportion of each T cell subset in blood was compared between patients with pSS (<i>n</i>=30) and healthy controls (HC) by flow cytometry (<i>n</i>=20). 3) The proportion of each T cell subset between blood and LSG was evaluated in patients with pSS by flow cytometry (<i>n</i>=7). 4) Based on the above results, by focusing on Tfh cells, Tfh-related gene mRNA expressions (CXCR5, Bcl6, TGF-β, IL-6, IL-12, IL-21) were evaluated in LSG of pSS (<i>n</i>=11) and HC (<i>n</i>=3). 5) The conditions of Tfh cell differentiation in pSS were examined. 6) Cytokine production from CD4<sup>+</sup> T cells cultured under determined Tfh cell differentiation condition in pSS were examined. 7) pSS derived peripheral CD4<sup>+</sup> T cells were co-cultured with HC derived naïve B cells under Tfh cell differentiation condition, and effect on B cells differentiation was analyzed. <h3>Results:</h3> 1) LSG-infiltrating T cells, and blood Th1, Tfh1, and Tfh2 cells showed higher clonality than Th17, and Tfh17 cells (Figure 1). Blood Tfh1, and Tfh2 cells were the two most frequent subsets comprised by the same T cell clones infiltrating in LSG. 2) Blood Tfh subsets were all significantly increased in patients with pSS than in HC. Among Tfh subsets, both PD-1 and ICOS expression was highest in Tfh1 subsets. Furthermore, the proportion of PD-1<sup>+</sup>ICOS<sup>+</sup>Tfh1 cells correlated with titers of anti-nuclear antibody, anti-SS-A antibody, and anti-SS-B antibody in pSS. 3) The proportions of memory Tfh subsets, especially Tfh1, was significantly increased in LSG compared with matched peripheral blood in pSS. 4) Expression levels of CXCR5, IL-6, IL-21, and TGF-β in LSG were significantly higher in pSS than HC. TGF-β positively correlated with CXCR5 expression in pSS. 5) CD4<sup>+</sup> T cells cultured under CD3/28 and TGF-β stimulation significantly increased CXCR5 expression, and Tfh1 population. 6) Production of IL-21, IL-2, and TNF-α were significantly increased after CD3/28 and TGF-β stimulation. 7) HC derived naïve B cells after co-culturing with pSS derived CD4<sup>+</sup> T cells, under Tfh differentiation condition (CD3/28 and TGF-β stimulation) expressed higher CD19, and CD19<sup>+</sup>CD38<sup>+</sup> B cell population was increased. <h3>Conclusion</h3> Tfh1 cells in blood not only frequently showed high clonal expansion, but also highly shared the same TCRαβ with LSG-infiltrating T cells in pSS. Tfh1 cell proportion was expanded among pSS at both peripheral blood and LSGs, and furthermore, they positively correlated with autoantibody production. They proliferated under TGF-β-enriched environment, such as seen in LSG of pSS. Thus, we conclude that blood Tfh1 subsets has the potential to reflect inflammatory organ immune environment, possibly taking a role on autoantibody production at LSG. <h3>Reference</h3> [1]Joachims ML, et al. Single-cell analysis of glandular T cell receptors in Sjögren's syndrome. <i>JCI Insight.</i> 2016 Jun 2;1(8):e85609 <h3>Acknowledgements:</h3> NIL. <h3>Disclosure of Interests</h3> None Declared.